Stepping mechanism for electromechanical counters



Jan. 3, 1967 R. E. EINEM ETAL 3,295,382

STEPPING MECHANISM FOR ELECTRO MEGHANIGAL COUNTERS 2 Sheets-Sheet 1 Original Filed May 16, 1965 Fla.

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STEPPING MECHANISM FOR ELECTRO-MECHANICAL COUNTERS Original Filed May 16, 1963 2 Sheets-Sheet 2 \NVENTORS Reese-r Bimmm F ENNQ A Kv EF e Y A United States Patent 3,295,382 STEPPING MECHANISM FOR ELECTRO- MEtIHANlCAL COUNTERS Robert E. Einem, Emmet Township, Dodge County, and Enno A. Knief, Watertown, Wis., assignors to Durant Manufacturing Co., Milwaukee, Wis, a corporation of Wisconsin Original application May 16, 1963, Ser. No. 284L786, now Patent No. 3,238,359, dated Mar. 1, 1966. Divided and this application Oct. 22, 1965, Ser. No. 501,893

6 Claims. (Cl. 74-142) This invention pertains to improved high speed electromechanical counters of the type adapted to count the number of input pulses and to indicate such number by visual and/ or electrical readout means.

This application is a division of copending application Serial No. 280,786, filed May 16, 1963, now Patent 3,238,359.

The principal object of this invention is to provide an improved electromechanical counter which will be more efficient and which will have a substantially longer service life than similar counters known heretofore.

The novelty of this invention lies in a new stepping mechanism design which permits easy accurate adjustment of the preload of the biasing means.

Further the novelty of this invention lies in the particular construction of the stepping mechanism and the drive pawl as will be more fully understood from the detailed description found in the specification.

The basic components of a counter embodying the present invention are a number wheel, a stepping mechanism having a ratchet wheel and an electro-magnet actuated drive pawl. The number wheel and the ratchet wheel, as shown in detail in said copending application Serial No. 280,786 may carry wiper blades which cooperate with specially designed printed circuitry. The design of the stepper mechanism is such that the pawl is cocked during the application of voltage to the electromagnet and only engages and advances the ratchet wheel and thus the number wheel after the voltage in the electro-magnet drops.

Other objects and advantages will be pointed out in or be apparent from, the specification and claims, as will obvious modifications of the single embodiment shown in the drawings, in which:

FIG. 1 is a plan view of the stepping mechanism and the number wheel of a counter embodying the present invention, the parts being mounted to one of the two side panels of the counter housing,

FIG. 2 is a side view of the structure shown in PEG. 1 with the other side panel being operably positioned over the stepping mechanism whereby there may be a contact between wiper blades which may be carried by the mechanism and a printed circuitry which may be carried on the inside face of the other side panel,

FIG. 3 is a plan view similar to FIG. 1 showing the pawl of the stepping mechanism in a cocked position,

FIG. 4 is a View taken on line 4-4 of FIG. 5,

FIG. 5 is a view taken on line 5-5 of FIG. 1 and showing the armature plate in cross section,

FIG. 6 is a detail view of the yoke spring, and

FIG. 7 illustrates the yoke spring action showing the yoke spring in an exaggerated tilted position.

Stepping mechanism, indicated generally at 23, embodying the present invention is mounted on a side panel 14 of a nonmagnetic material. This panel also carries a number wheel 24. An opposite side panel 16 is of a dielectric material and, as shown in said application Serial No. 280,786, may carry specially designed printed circuits which are contacted wiper blades which may be carried by such stepping mechanism and number wheel.

3,295,382 Patented Jan. 3, 1967 The stepping mechanism is actuated in response to the application of input pulse voltage to the electro-magnet, shown generally at 42, and is adapted to advance the ratchet wheel 40 and the number wheel 24 after the voltage in the electro-magnet has dropped. The electromagnet is comprised of a U-shaped laminated core 44 and coils 46 which are connected in series and which have a positive lead 48 and a negative lead 50 adapted to be connected in an external circuit (not shown) which produces the input pulses to be counted. Thus voltage is applied to the electro-magnet during the reception of the input pulses and drops during the time intervals between the input pulses. The electro-magnet is mounted on the side panel 14 by means of screws 52.

The number wheel 24 is rotatably carried on a stub shaft 54 by means of a hub 56 on which a wiper may be mounted. The number wheel is mounted for rotation with the ratchet wheel 40 by means of engaging gears 62 and 64 which are integral with their respective wheels. The number wheel is geared to the ratchet wheel at a 2:1 ratio, such that one-half revolution of the ratchet wheel will equal one revolution of the number wheel. The ratchet wheel is rotatably mounted on stub shaft 66 by a hub 68 on which a wiper may be mounted.

The ratchet teeth 74 are engaged by a drive pawl 76, which is pivotally secured to a drive arm 78 by means of a pin 80 and which is biased against the ratchet wheel by a spring 82. The drive arm is pivotally secured to the side panel by a drive arm pivot 84. An armature plate 86 is pivotally connected to the drive arm by a bracket 88 and a pin 90. The bottom face of the armature plate is provided with a mylar film 87 which serves to space the armature plate from the cores 44 to thereby relieve the residual magnetism of the armature.

Upon reception of an input pulse by the counter, the input pulse voltage is applied to the coils 46 causing the armature plate 86 to be pulled against the magnetic cores 44 of the electro-magnet. The downward pull of the armature causes the drive arm 78 to pivot in a counterclockwise direction around pin 84 (as seen in FIG. 1), thereby causing the boss 92 of the drive pawl '76 to slide backwardly over ratchet tooth 74 and assume the position as shown in FIG. 3. During this motion of the pawl, the ratchet is restrained from backward movement by a hairspring 94. The mechanism remains in this cocked position throughout the application of the input pulse voltage to the electro-magnet 42. As the voltage in the electro-magnet drops at the end of the input pulse, the armaure 86 is released and the drive arm is caused to travel upwardly and in a clockwise direction around pin 84 in response to the bias of yoke spring 96 which engages the armature bracket 88 and the two yoke spring cams 98. During this motion the boss 92 engages the: ratchet tooth 74 and advances the ratchet wheel by 18 thereby ausing a travel of 36 by the number wheel. This travel, of course, causes the number wheel to expose a higher numeral.

The drive pawl is provided with two bosses, 92 and 109, which cooperate to perform the function usually accomplished by use of two separate pawls, i.e. to limit the advancement of the ratchet to one predetermined step. The cooperation is as follows: upon release of the armature from the electro-magnet the boss 92 is moved to engage the ratchet tooth '74 and thereby advance the ratchet wheel, and the boss 100 is simultaneously moved to engage the top face of another one of the ratchet teeth thereby preventing motion of the ratchet wheel relative to the pawl. When the armature comes to rest in the free position shown in FIG. 1, any further forward motion of the ratchet wheel (as caused by inertia or some external force) is prevented by boss 100. This cooperation, of

.3 course, insures that the wheels only travel the intended increment per input pulse.

It is important to note that the location of the boss 100 is such that the force which would be exerted thereon, if the ratchet wheel were attempted to be rotated without the actuation of the armature 86, will tend to press boss 92 into together engagement with the wheel.

Further, this force will be in such a direction that it will not have a component (or component of suificient magnitude) in a direction (counterclockwise in FIG. 1) around pin 84- which would aid in pivoting the drive arm 78 away from the ratchet wheel. In fact, the illustrated embodiment shows the boss 100 so located that the turning force of the ratchet will be in a direction tending to pivot drive arm 78 yet closer to the wheel.

An important part of the stepping mechanism design is the biasing means incorporated therein. The biasing means comprise the yoke spring 96 and a preload spring 102, both springs being operable to resist the downward movement of the armature in response to the voltage applied to the coils of the electro-magnet and also, of course, operable to move the armature away from the cores 44 and to impart motion to the drive arm and pawl to thereby advance the ratchet wheel. The preload spring is secured to the drive arm 78 and contacts cam 104. Cam 104 and cams 98 are eccentrics which may be rotated to vary the bias of their respective springs.

The preload of the armature is determined both by the position of cams 98 in respect to the yoke spring 96 and by the position of cam 104 in respect to the preload spring 102. Cams 98 provide the rough adjustment and cam 104 provides the fine adjustment. The advantages of providing the preload spring 102 are two-fold; first the fine adjustment requires the manipulation of only a single cam, and second the preload spring permits the use of a lighter and therefore more accurate yoke spring.

It is of note that the distance between cam 104 and the drive arm pivot 84 is substantially greater than the distance between the pivot 84 and the pin 90. In the illustrated embodiment the ratio of the distances is approximately 5:1. The significance of this mechanical advantage is that the preload spring 102 performs the work equivalent to a spring positioned as the yoke spring 96 (essentially having no mechanical advantage) yet only has one-fifth (at ratio 5:1) of the spring force of such equivalent spring. This feature thus also permits the use of a lighter and therefore more easily adjustable spring.

The yoke spring 96 is of a design which insures parallel motion (to faces of cores 44) of the armature plate 86 as it is pulled towards the cores 44 of the electro-magnet. Such motion is very desirable since variance in the time between the seating of the armature on one core and the other would cause a serious rubbing of the contact face of the armature and result in its accelerated wear. Although in assembling of counters of this type, the cores 44 are placed an equal distance from the armature 86, unequal magnetic forces caused by normal variations in the coils or in the air gap spacings will tend to pull one side of the armature ahead of the other side. The yoke spring has been designed to counteract this unequality in force. This counteraction is attained by the particular angulation of the yoke spring 96. As best seen in FIG. 6, the contour of the spring is somewhat bird-shaped, having two upwardly inclined portions 108 which engage the armature bracket 88, and having two downwardly inclined shorter end portions 110 which contact and exert a bias against the yoke spring cams 98. Each spring end 110 is generally in a line which points towards the armature pin 90. In order to prevent one end of the armature plate from moving faster towards the electro magnet than the other end, the yoke spring 96 is of a design which responds to any pivotal motion of the armature around pin 90 (which would necessarily result when one end travels faster than the other) to decrease the spring bias exerted on 111? slower travelling side of the armature plate and to increase the bias on the faster travelling side. The result of decreasing the bias on the slower side is that correspondingly less force is required to advance that side of the armature towards its core and thereby the weaker core of the electro-magnet is able to pull the armature at the same speed as the stronger side. The principle is illustrated in the exaggerated example shown in FIG. 7. In this example the right hand coil is shown as exerting a smaller magnetic force than the left hand coil and, therefore, causing the left hand side to advance further (faster) towards the left coil. This disparity in travel has caused the armature bracket 88 to pivot around pin 90, thereby causing the right spring end to lift off its cam, and thus necessarily offer less resistance than the left hand spring end 110. In turn the left hand spring end is forced against the left cam 98, thereby causing a corresponding increase in the resistance offered to the left end of the armature plate which results in slowing down of this side of the armature. If should be understood that in practice the spring ends do not move away from the cams, but only that thespring ends automatically adjust themselves so that the motion of the armature on the stronger coil side will be resisted by an increased spring bias and the motion on the weak c-oil side will be resisted by a decreased bias, thereby permitting both ends of the armature to travel at the same speed towards the cores despite the disparity in magnetic forces between the two coils. By inclining the spring ends 110 in a direction generally pointing towards the pin 90, the pivotal motion of the armature will also cause an equal angular movement of the spring ends in respect to the armature and thus assure maximum response to the disparity in magnetic forces.

Only one embodiment of the present invention has been illustrated and described, but it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What is claimed is:

1. A stepping mechanism comprising,

electromagnetic means adapted to be connected to a source of input pulses and to be energized during reception of the input pulses,

an armature in operative relation to said means and provided with a bracket,

a pivoted drive arm having a pivotal connection with said bracket,

a pawl carried by said drive arm,

a ratchet wheel advanced by said pawl,

a yoke spring for biasing siad armature and bracket away from said means and having end sections inclined in a direction towards said pivotal connection and being engaged by said bracket betwen said end sections, and

support means for said end sections, said armature and bracket being pulled in opposition to the bias of said yoke spring towards said electro-magnetic means during energization of said means, and being moved in a direction away from said elect-r-o-magnetic means by said yoke spring when said electro-magnetic means is de-energized, said end sections stabilizing the motion of said armature.

Z. A stepping mechanism according to claim 1 wherein said support means comprise eccentric cams which are rotatable to vary the bias of said yoke spring.

3. A stepping mechanism according to claim 2 having a preload spring mounted to oppose the movement of said armature bracket towards said electr-o-magnet, one end of said preload spring being positioned adjacent a stationary cam member, and said calm member being adjustable to vary the bias of said preload spring.

4. A stepping mechanism according to claim 3 wherein said preload spring is so mounted as to cause during movement of said armature greater movement of said one end than the corresponding movement of said yoke spring, thereby providing a mechanical advantage to said preload spring.

5. A stepping mechanism according to claim 2 wherein said electro-magnet means comprise two coils spaced substantially an equal distance firom said bracket, said yoke spring being responsive to discrepancies in magnetic force of said coils to decrease the bias on the armature portion overlying the weaker coil and to increase the bias on the armature portion overlying the stronger coil.

6. A su-bassembly for a stepping mechanism adapted to compensate for discrepancies in magnetic force between the coils of an electro-magnet of the mechanism comprising,

a pawl drive arm,

an armature bracket having a pivotal connection to said pawl drive anm,

an armature fixed to said armature bracket, and

References Cited by the Examiner UNITED STATES PATENTS Baughan 74-442 Richter 74-142 Solinski 74112 White et a1. 267-1 X Blattner 74-142 Jenny et al. 2 671 X MILTON KAUFMAN, Primary Examiner.

FRED C. MATTERN, Examiner.

D. H. THIEL, Assistant Examiner. 

1. A STEPPING MECHANISM COMPRISING, ELECTRO-MAGNETIC MEANS ADAPTED TO BE CONNECTED TO A SOURCE OF INPUT PULSES AND TO BE ENERGIZED DURING RECEPTION OF THE INPUT PULSES, AN ARMATURE IN OPERATIVE RELATION TO SAID MEANS AND PROVIDED WITH A BRACKET, A PIVOTED DRIVE ARM HAVING A PIVOTAL CONNECTION WITH SAID BRACKET, A PAWL CARRIED BY SAID DRIVE ARM, A RATCHET WHEEL ADVANCED BY SAID PAWL, A YOKE SPRING FOR BIASING SAID ARMATURE AND BRACKET AWAY FROM SAID MEANS AND HAVING END SECTIONS INCLINED IN A DIRECTION TOWARDS SAID PIVOTAL CONNECTION AND BEING ENGAGED BY SAID BRACKET BETWEEN SAID END SECTIONS, AND SUPPORT MEANS FOR SAID END SECTIONS, SAID ARMATURE AND BRACKET BEING PULLED IN OPPOSITION TO THE BIAS OF SAID YOKE SPRING TOWARDS SAID ELECTRO-MAGNETIC MEANS DURING ENERGIZATION OF SAID MEANS, AND BEING MOVED IN A DIRECTION AWAY FROM SAID ELECTRO-MAGNETIC MEANS BY SAID YOKE SPRING WHEN SAID ELECTRO-MAGNETIC MEANS IS DE-ENERGIZED, SAID END SECTIONS STABILIZING THE MOTION OF SAID ARMATURE. 